After doing some work on NA 993s, it is clear the these engines appear to be set about 1-1/2"s further forward (as I said seems to be). On the NA, there is WAY more room to work on the fan, and the offset on the passenger side for the AC clutch is equally further forward. I took some quick crude measurements of the fan housing (as I thought maybe with the added supports for the intercooler this added to the housing) and they seem to be almost the same size. So then is the TT engine set further back? I really can't see how with the transaxle and all, but why would these other components be offest to the rear so much making everthing to work on more difficult???

 

That is very interesting, I wonder if it is the same on a 993 C4S. Good
thing is the engine weight is better distrubuted, closer to the rear wheels.

John

 

No John, I also thought the same thing and checked on a C4S that was here. Definitely just a Turbo thing. But it is a good 1-1/2" difference for the fan and the air compressor being closer to the back of the engine compartment.

 

Bob, I would agree with You when I look at them side by side they look to be set back more(TT) and the Motor mount is different. I will try to figure out why and llet You know.

 

Yes, your observations are correct. The engine is back further in the Turbo by 40mm or so.

The distance between the the engine mount bolt holes and the trans mount bolt holes is fixed by the design of the chassis. The C4S and Turbo therefore are no different in this respect.

The Turbo transaxle includes a larger diameter ring gear for the differential. This extends the length of the transmission by (you guessed it!) 40mm. Since now the length of the engine/trans package has gained 40mm, 40mm must be removed from somewhere else.

The rear engine mount crossmember on the N/A engines spaces the engine forward about 40mm. The Turbo crossmember is flatter and does not have the 40mm spacing.

This situation is not unique to 993s. All 911 Turbo's since the 70's have had the larger ring gear and therefore the more rearward placed engine.

Nowadays, all the GT3 based 996 engines (Turbo, GT3, Cup, and GT3R) all use the Turbo size ring gear. The basic 996 has a shorter engine/trans package than a 993, so the 996 chassis is modified to recieve the longer package as well. All these 996s have really extreme rearward engine placement and therefore weight distribution.

Everybody asks why Porsche won't build a 996 Turbo for racing. It wouldn't work. The rear wheels would carry probably 68% of the car's weight. Getting the car to handle right with rear weight like that would be impossible.

 

Chris;

For what it's worth, I appreciate your knowledge of facts on the Turbo's (993) I have lately been struggling with the fact that are cars are setting on the back burner for knowledge and developement.